1. Technical Field
The present invention relates to an image display device.
2. Related Art
Rear-projection type image display devices (rear projectors), projecting color light from the rear side of a screen, are known as one example of an image display device (projector) projecting colored light containing image information, generated by a liquid crystal device or other spatial light modulation section, onto a screen via a projection system. In Japanese Unexamined Patent Application, First Publication No. 2003-185969, a stereoscopic image display device is disclosed projecting colored light with different polarization directions onto a screen, causing the projected image to be recognized by viewers as a stereoscopic image. Furthermore, Japanese Unexamined Patent Application, First Publication No. 2002-72359 discloses an image display device which combines a plurality of projected images of a projector side-by-side on a screen to present a large-size image.
However, in the above-described image display devices, the object plane of the projection system must be made to coincide with the light emission face of the spatial light modulation section, and the image plane of the projection system must be made to coincide with the screen, so that the light emission face of the spatial light modulation section and the screen are in a conjugate positional relation with respect to the projection system. In the technology of the prior art, a configuration is adopted in which a combining system, including a dichroic prism or similar, is provided between the spatial light modulation section and the projection system, and so a distance between the projection system and the light emission face of the spatial light modulation section (the backfocus of the projection system) must be secured sufficient to enable placement of the combining system. If the backfocus becomes too long, the distance between the projection system and the screen (the frontfocus of the projection system) also becomes long, and when using this image display device in a rear projector, this distance impedes efforts to reduce the size (reduce the thickness) of the rear projector. Furthermore, a long projection distance of the overall device has been necessary in order to enable application to large devices accommodating large projection spaces.